On Mon, Apr 12, 2021 at 09:30:19PM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git dev
> head:   fcdf3c34b7abdcbb49690c94c7fa6ce224dc9749
> commit: a6c75eaf11032f4a3d2b3ce2265a194ac6e4a7f0 [13/28] ext4: add mballoc stats proc file
> config: um-randconfig-r022-20210412 (attached as .config)
> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> reproduce (this is a W=1 build):
>         # https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit/?id=a6c75eaf11032f4a3d2b3ce2265a194ac6e4a7f0
>         git remote add ext4 https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git
>         git fetch --no-tags ext4 dev
>         git checkout a6c75eaf11032f4a3d2b3ce2265a194ac6e4a7f0
>         # save the attached .config to linux build tree
>         make W=1 ARCH=um 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All errors (new ones prefixed by >>):
> 
>    /usr/bin/ld: kernel/fork.o: in function `mm_init':
>    fork.c:(.text+0x1294): undefined reference to `atomic64_set_386'

This appears to be a problem in the UM architecture.  Tested using
linux.git (without any of the ext4.git changes for the next merge
window), I'm seeing very similar failures on commit 50987beca096
("Merge tag 'trace-v5.12-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace")

See attached makelog and config.gz.

Fortunately the configs used by kunit tests don't seem to technical
the issue.  So it's not something I'm going to care about, but perhaps
it's something the ARCH=um folks might want to address?

					- Ted